The present invention is related to a novel solenoid valve, with application in general to auxiliary power systems. For example, it may be used in an auxiliary power system employing a vapor engine for assisting in driving a primary engine, such as an internal combustion engine and the like, using available heat, typically generated by the primary engine.
Internal combustion engines are probably the largest single user of petroleum and its products. Mainly, these engines are used in automobiles and trucks, although many in stationary form are used in industry. Power plant engineers have long been aware that the internal combustion engine is relatively inefficient compared to other power sources such as electric motors. Moreover, presently the overall efficiency of automobile and truck engines is being decreased even more by requirements for emission controls in order to protect the environment. It is common, for example, for present automobile engines to operate at an overall efficiency of approximately 15 percent, and in many cases even lower.
Textbooks concerned with today's internal combustion engines indicate that out of the total power available in the fuel consumed, approximately 30 percent of the energy (gross) actually produces power, approximately 30 percent goes out the exhaust pipe in the form of waste heat, and approximately another 30 percent is lost through the radiator and the cooling system in the form of waste heat. About 10 percent is used for engine accessories such as the fan, alternator, transmission, etc. Of the 30 percent of the heat energy that produces power, actually, only about half reaches the road, in cases where the engine is driving a car or truck. Because literally millions of automobiles and trucks in use in the world at the present time consume hundreds of millions of gallons of gasoline and diesel fuel annually, obviously, an improvement in the overall efficiency of the internal combustion engine is very meaningful.
Heretofore, a number of proposals have been made for increasing the efficiency of an internal combustion engine using steam power generated from the heat of the internal combustion engine. In a number of such proposals, a piston driven by steam is connected directly to the same crankshaft as the pistons in the internal combustion cylinders. This type of arrangement is complex, costly to manufacture and is itself inefficient in that it presents an additional load on the internal combustion engine due to friction when insufficient steam is generated to drive the steam pistons or is valved from the steam cylinders as during idling. Also, the arrangement is not readily adaptable to existing internal combustion engines. Further, the use of steam must rely principally on the heat in the exhaust system and largely neglects the heat lost in the radiator system.
In another prior known proposal, a separate steam engine is described as being coupled, as by a universal jointed shaft, to the crankshaft of an internal combustion engine. Gauges and the like are provided for measuring the steam pressure and water temperature and manual valving means are provided for controlling the steam flow to the steam engine. Safety valve means are also provided for venting steam to the atmosphere when excessive steam pressure develops in the system.
While more easily adaptable to existing internal combustion engines than the previously described prior known arrangements, the latter system also suffers from certain undesirable inefficiencies. The use of a universal jointed shaft and the like for coupling the steam engine directly to the crankshaft of the internal combustion engine, for example, will also result in loading down the internal combustion engine at times when the steam engine is developing insufficient output power to drive the internal combustion engine. The use of gauges and manual steam control valves provides for further inefficiencies in that they require the attention of the operator which is distracting particularly when the system is employed to power a motor vehicle. The nature of the safety valve means employed in this arrangement is also undesirable in that it is necessary to replenish the water lost during blow-off. Clearly, therefore, a fully automatic closed auxiliary system which is relatively inexpensive, and readily adaptable to existing internal combustion engines, is preferable.
An object of the invention is to provide a solenoid valve for use in a control array for a system having a primary engine and an auxiliary vapor engine operating from normally wasted heat of the primary engine, so that the flow of fluid to the vapor engine is governed by the temperature of the cooling circuit for the primary engine, including the initiation of such flow only after the primary engine has been warmed sufficiently for its basic efficiency.
Another object of the invention is to provide a solenoid valve, wherein the armature is shaped so as to give a power output that is a substantially linear function of the current through the field coil.